Electric winch device

Abstract

An electric winch device including an electric motor that rotates a winch drum in a hoisting direction, and generates regenerative electric power when a rotation of the winch drum in a lowering direction is transmitted to the electric motor, a transmission device that transmits the rotation between the electric motor and the winch drum, a power calculating section that calculates power of the target object by freefall, and a control section that controls an operation of the transmission device. When the power calculated by the power calculating section exceeds reference electric power, the control section causes the transmission device to change the transmission rate of the rotation to a transmission rate at which the regenerative electric power generated by the electric motor is equal to or smaller than the reference electric power.

The invention claimed is: 
     
       1. An electric winch device provided in a crane to perform hoisting and lowering of a target object, the electric winch device comprising:
 a winch drum which rotates for the hoisting and the lowering of the target object; 
 an electric motor which rotates the winch drum in a hoisting direction during the hoisting of the target object, and generates regenerative electric power when a rotation of the winch drum in a lowering direction during a freefall of the target object is transmitted to the electric motor; 
 a transmission device which transmits the rotation between the electric motor and the winch drum, the transmission device having a variable transmission rate which is a rate of transmission of the rotation of the winch drum in the lowering direction during the freefall to the electric motor; 
 a power calculating section which calculates power of the target object by the freefall; and 
 a control section which controls an operation of the transmission device for changing the transmission rate, wherein 
 when the power calculated by the power calculating section exceeds reference electric power set according to allowable electric power of the electric motor, the control section causes the transmission device to change the transmission rate of the rotation from the winch drum to the electric motor to a transmission rate at which the regenerative electric power generated by the electric motor is equal to or smaller than the reference electric power. 
 
     
     
       2. The electric winch device according to  claim 1 , further comprising:
 a brake operation section which is operated to stop the freefall of the target object; and 
 a speed deriving section which successively derives falling speed of the target object, wherein 
 the power calculating section calculates, on the basis of falling speed derived by the speed deriving section at timing when the operation of the brake operation section for stopping the freefall of the target object is performed, power of the target object at the timing as the power of the target object by the freefall. 
 
     
     
       3. The electric winch device according to  claim 1 , further comprising:
 a brake operation section which is operated to stop the freefall of the target object; and 
 a distance deriving section which derives a maximum distance of the freefall of the target object at a time point of start of the freefall of the target object, wherein 
 the power calculating section calculates, on the basis of the maximum distance derived by the distance deriving section, upper limit power of the target object during the freefall as power of the target object by the freefall, and 
 when the upper limit power calculated by the power calculating section exceeds the reference electric power after the operation of the brake operation section for stopping the freefall of the target object is performed, the control section causes the transmission device to change the transmission rate of the rotation from the winch drum to the electric motor to a transmission rate at which the regenerative electric power generated by the electric motor is equal to or smaller than the reference electric power. 
 
     
     
       4. The electric winch device according to  claim 3 , wherein
 the power calculating section calculates predicted maximum speed, which is falling speed which the target object reaches when the target object free-falls by the maximum distance derived by the distance deriving section, and calculates predicted maximum power, which is power of the target object at a time when the target object reaches the calculated predicted maximum speed, and 
 when the predicted maximum power is equal to or smaller than the reference electric power, the control section causes the transmission device to transmit the rotation of the winch drum to the electric motor at a transmission rate of 100%. 
 
     
     
       5. The electric winch device according to  claim 1 , wherein
 the transmission device includes:
 a first rotating section which rotates integrally with the winch drum; 
 a second rotating section which rotates together with a driving shaft of the electric motor; and 
 a changing device which changes a coupling state between the first rotating section and the second rotating section, and 
 
 when the power calculated by the power calculating section exceeds the reference electric power, the control section causes the changing device to change the coupling state between the first rotating section and the second rotating section to a coupling state in which the first rotating section slips relative to the second rotating section so that rotating speed of the second rotating section is lower than rotating speed of the first rotating section. 
 
     
     
       6. The electric winch device according to  claim 5 , wherein the transmission device is a wet clutch. 
     
     
       7. The electric winch device according to  claim 1 , wherein
 the transmission device includes:
 a first rotating section which rotates integrally with the winch drum; 
 a second rotating section which rotates together with a driving shaft of the electric motor; and 
 a switching device which switches coupling and separation between the first rotating section and the second rotating section, and 
 
 when the power calculated by the power calculating section exceeds the reference electric power, the control section causes the switching device to separate the first rotating section and the second rotating section from each other to thereby reduce the transmission rate by the transmission device to 0%. 
 
     
     
       8. The electric winch device according to  claim 7 , wherein the transmission device is a wet clutch.